Tylencholaimus singaporensis, Ahmad, Wasim, 2010

Ahmad, Wasim, 2010, Three new and a known species of Tylencholaimoidea (Nematoda: Dorylaimida) from Singapore, Zootaxa 2505, pp. 51-64 : 59-63

Tylencholaimus singaporensis n. sp.

( Figs. 5 , 6 )

Measurements: Table 2 .

Description. Female: Body slightly curved ventrad upon fixation. Outer cuticle smooth, inner cuticle distinctly striated, loose, 1.0 µm thick at mid body and 1.5–2 µm on tail. Lateral chords about one-third of body width at mid body. Lateral, dorsal and ventral body pores indistinct.

Lip region cap-like, offset by constriction, about one-half as wide as high or about one-third as wide as body width at neck base. Lips somewhat separate; papillae slightly raised. Amphids stirrup-shaped, their aperture occupying about one-third of the lip region width. Odontostyle typical of the genus, about 0.75–0.85 times lip region width long, its aperture about one-third of its length. Guiding ring ‘single’, at 0.6–0.8 times lip region width from anterior end. Odontophore rod-like with small but distinct basal knobs, 1.1 times the odontostyle length. Nerve ring encircling the anterior slender part of pharynx at 35–40% of neck length from anterior end. Pharynx consists of a slender and weakly muscular part which expands abruptly into a cylindrical basal bulb occupying about 43–45% of total neck length. Cardia short, conoid, about one-forth to one-third of corresponding body width long. Pharyngeal gland nuclei located as follows: D = 60–63%; AS 1 = 28–32%; AS 2 = 40–43%; PS1 = 72–74%; PS2 = 73–75%

Genital system mono-prodelphic. Anterior genital branch well developed; ovary reflexed, measuring 33– 72 µm, with oocytes arranged in a single row except near tip. Oviduct joining the ovary subterminally, measuring 32–50 µm long. A weak sphincter present at oviduct-uterus junction. Uterus a small tube, measuring 25–30 µm. Vulva transverse. Vagina anteriorly directed, about half of corresponding body width deep; pars proximalis vaginae 5–6 µm with thickened walls encircled by circular muscles; pars distalis appearing as two rod-shaped refractive area measuring 2.5 x 1.7 µm. Prerectum about 2.1–2.6 anal body widths long. Rectum about 0.68–0.75 anal body width. Tail short, hemispheroid with rounded terminus, 0.7– 0.9 times anal body width long with a distinct terminal caudal pore.

Male: Not found.

Tylencholaimus singaporensis n. sp. T. intermedius Characters Holotype female Paratype females females

n 5 4

Type habitat and locality: Soil around roots of forest trees from Kent Ridge Park near the National University of Singapore; Collected on September 1, 2003.

Diagnosis and relationships: Tylencholaimus singaporensis n. sp. is characterised by having 0.35–0.47 mm long body; distinctly offset, cap-like lip region; 4.5–5.5 µm long, slender odontostyle; simple rod-like odontophore with small but distinct basal knobs; pharynx consists of a slender and weakly muscular anterior part which expands abruptly into a cylindrical basal bulb; mono-prodelphic female genital system with no post uterine sac, two rod-shaped thickening in vagina, and short hemispheroid tail with distinct terminal caudal pore.

In the Tylencholaimus De Man, 1876 species group with mono-prodelphic female genital system, absence of perioral disc and anterior part of pharynx weakly muscular and expanding abruptly into basal bulb, the new species closely resembles T. rumjhumi Khan & Laha, 1983 but differs in having smaller and robust body ( vs L= 0.48–0.65 mm; a= 21.5–26.5); smaller amphid ( vs 1/3 lip region width wide); shorter odontostyle ( vs odontostyle 6–7 µm); comparatively shorter pharynx ( vs b=3.1–3.5); longer expanded part of pharynx ( vs 41%), presence of rod-shaped thickening in vagina ( vs absence), and in having rounded tail with terminal caudal pore ( vs tail dorsally convex conoid without terminal caudal pore).

The new species is also close to T. vigil Andrássy, 1959 but differs in having smaller body ( vs 0.57–0.61 mm); smaller amphids ( vs 30–40% of corresponding body width wide), shorter odontostyle+odontophore length ( vs odontostyle+odontophore length 14–15 µm); smaller expanded part of pharynx ( vs 56–60%); more posterior vulva position ( vs V= 67.8–68.5); presence of clear thickening in vagina ( vs no thickening in vagina); shorter prerectum ( vs prerectum 3.2 anal body widths long) and differently shaped tail ( vs tail conoid without terminal caudal pore).

Etymology: The species epithet singaporensis refers to Singapore.

Figures

FIGURE 5. Tylencholaimus singaporensis n. sp. A: Entire female. B: Anterior region. C: Expanded part of pharynx. D: Female genital system. E: Female posterior region.

FIGURE 6. Tylencholaimus singaporensis n. sp. A-B: Anterior region. C: Expanded part of pharynx. D: Vulva region showing thickened pars distalis. E: Expanded part of pharynx. F: Female posterior region. (scale bar = 10 um)

Tables

TABLE 2. Morphometrics of Tylencholaimus singaporensis n. sp. and T. intermedius Peňa Santiago & Coomans, 1996. All measurements in µm (except L) and in the form: mean standard deviation (range).

L	378	411 ± 50 (349–470)	486 ± 22 (457–581)
a	22.8	23.7 ± 2.44 (21.5–26.5)	32.5 ± 2.3 (30–36)
b	2.6	2.7 ± 0.33 (2.3–3.2)	3. ± 0.07 (3.1–3.3)
c	43	39.5 ± 1.2 (38.5–41)	31 ± 1.9 (28.5–34)
c`	0.73	0.81 ± 0.12(0.70–0.96)	1.4 ± 0.05(1.4–1.5)
V	79	75 ± 2 (73–76)	51 ± 1(48.5–51.5)
G1	21	21 ± 5 (14–26)	-
G2	-	-	16 ± 1(13.5–17)
Lip region width	6.0	6.1 ± 0.3 (5.5–6.5)	6.4 ± 0.36(6–7)
Lip region height	3.0	3.05 ± 0.3 (2.5–3.0)	2.1 ± 0.17(2–2.4)
Amphid aperture	2.0	2.2 ± 0.23 (2.0–2.5)	3 ± 0
Odontostyle length	5.0	5.0 ± 0.38 (4.8–5.0)	7.2 ± 0.18(7–7.5)
Odontophore length	5.5	5.5	7.4 ± 0.18(7–7.5)
Guiding ring from ant. end	5	4.6 ± 0.23(4.5–5.0)	4.6 ± 0.38(4–5)
Nerve ring from ant. end	57	58 ± 2.4(54.5–62)	62 ± 4.3(55–66)
Neck length	145	148 ± 5.3(138–155)	155 ± 10.4(138–165)
Expanded part of pharynx	62	66 ± 3.0(62–71)	58 ± 5.6(50–65)
Cardia length	5.6	5.2 ± 0.89(4–6.5)	4.6 ± 0.47(4–5)
Body width at neck base	16	17 ± 0.56(15–17)	15 ± 1(14–16)
Body width at mid body	16.5	17 ± 0.86(16–18.5)	15 ± 1.46(13–17)
Body width at anus	12	13 ± 0.6(12–13.6)	11 ± 0.75(10–12)
Anterior genital branch	77.5	83 ± 13.5(66–103)	–
Posterior genital branch	-	-	75 ± 4.2(69–81)
Vaginal depth	7	6.4 ± 1.29(6–8)	6.4 ± 1.29(6–8)
Vulva from anterior end	298	308 ± 30.7(268–344)	246 ± 8(234–255)
Prerectum length	35	26.5 ± 11.5(25.5–28)	43 ± 6(35–52)
Rectum length	9	11 ± 0.77(10–12)	13 ± 3(8–16)
Tail length	8.8	10.4 ± 1.34 (8.8–12)	16 ± 1 (14–17)